Modern power semiconductor modules, which are the starting point of this invention, are modules without a base plate. In line with the generic type, said modules have a housing, a ceramic substrate with metal laminations which are designed to match the circuitry and are arranged on said substrate, as are produced, for example, in accordance with the DCB (direct copper bonding) process; components, such as diodes, transistors, resistors or sensors for example, and also bonding connections for connecting the structured side of the chip-like, unenclosed power semiconductor components to further components and/or to the substrate and/or to connection elements, which lead to the outside, which components are fitted on said substrate in a cohesive manner by means of soldering.
Furthermore, an encapsulation compound comprising silicone rubber is preferably provided in order to insulate the individual components from one another.
Heat transfer between the substrate and the heat sink is a key variable for power semiconductor modules which directly determines the performance of said power semiconductor modules. The heat which is produced in the power semiconductor components during operation therefore has to be dissipated as efficiently as possible.
It has been found that, in particular, solder connections, of large surface area, to a heat sink can be controlled in respect of quality only with great difficulty, this having an adverse effect on the reliability and also the service life of the power semiconductor modules. Therefore, the assembly technology with pressure contact for thermally conductive connection of the module to a heat sink has proven highly advantageous for power semiconductor modules of this kind.
DE 10 2004 051 039 A1 discloses a power semiconductor module of which the cover serves firstly to introduce pressure and also to exert pressure onto the bonding feet of the wire bonding connections of the power semiconductor components. Said document further describes and shows prior art in which the housing cover forms dies with which the substrate is pressed against the heat sink. In this case, it is very difficult to adjust the introduction of pressure and the substrate may be damaged or the contact-connection is not established in a reliable manner.
A further objective is to provide a module which can be supplied in a substantially preassembled state and as far as possible only needs to be fitted on a heat sink without other preassembly steps at the intended fitting location.
There is therefore a need for a power semiconductor module with improved assembly, which is due to simplified assembly, together with efficient heat transfer from the power semiconductor component to the heat sink.